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Somewhat similar to the California Tortoiseshell (Nymphalis californica), but the Conmpton has a predominantly pale hindwing margin (and is larger), while that of californica is black. This is another species whose scientific name has received a complete makeover as a result of careful study by a number of researchers; the Compton Tortoiseshell was traditionally known as Nymphalis vau-album, but may be known as Roddia l-album in the future; it is more closely related to the commas (Polygonia) than members of the genus Nymphalis, and may represent an evolutionary linkage between these two groups (Nylin et al. 2001). For a complete review of the nomeclature changes, see Guppy & Shepard (2001). Bird et al. (1995) call AB populations ssp. j-album, while Guppy & Shepard (2001) treat them as the western watsoni. Layberry et al. (1998) do not recognize watsoni as a sufficiently distinct taxon, presumably because of minor differences between the two, and treat all Canadian populations as j-album. A review of this situation is in order.

The light green eggs are cylindrical and have 11 vertical ridges. Mature larvae are black dorsally and brown laterally, with black, branched spines and fine white markings (Guppy & Shepard 2001). The pale green pupae have pinkish spots and three pairs of golden-silver spots on the back (Guppy & Shepard 2001). The adults emerge in late summer and hibernate, with mating and egg-laying occuring in the spring. This tortoiseshell has irruptive population dynamics, and may be very rare or absent many years in a row, then appear abundantly for a year or two. When it is common, it can be found during the winter in unheated, outdoor shelters such as barns and outhouses. In suitable years, possibly when outbreaks occur, this species will also migrate beyond its normal breeding grounds.

In British Columbia, the only recorded larval hostplants are birches (Betula spp.) (Guppy & Shepard 2001). Adults prefer tree sap flows and mammal scat to flowers, and in outbreak years can form large mud-puddling congregations.

This species spans two continents, occuring across northern North America and also in Eurasia. It is found throughout most of non-arctic Canada and the northern United States (Opler 1999). May be a migrant to the northern- and southermost extents of its range; Opler (1999) depicts the northern Alberta records as migrants, but the Compton is found regularly there and there is no reason to believe these individuals represent migrants.